Iraqi officials are increasingly emboldened about their prospects of retaking the city of Mosul from the Islamic State terror group even though it puts them at odds with the U.S. assessment.

Neither they nor U.S. defense officials have been willing to put any sort of timeline on what promises to be a complex operation to push IS out of Iraq's second-largest city. Still, with each day that passes Iraq's confidence seems to grow.

"I believe that this will happen sooner or later because the Iraqi Army is gaining," Iraqi Foreign Minister Ibrahim al-Jaafari told VOA through an interpreter following his most recent trip to Washington.

Those steady gains, pushing IS out of about half of the territory it once held in Iraq, have come as Iraq Security Forces and Kurdish Peshmerga fighters march to a steady drumbeat of U.S. and coalition airstrikes.

Yet U.S. and coalition officials meeting in Washington last week voiced strong concerns about the dangers of the potential lag time between an initial military push into Mosul and follow-up operations to stabilize the city.

Before leaving Washington, Iraq's foreign minister tried to put such concerns to rest.

"The Iraqi government has prepared a plan," al-Jaafari told VOA late Friday. "It has a military phase, a services phase, and also a plan for the humanitarian response."

The plan, he said, puts heavy emphasis on preserving the city's infrastructure and key facilities "during the first phase of the operation and its aftermath" in order to maintain public services, or restart them as quickly as possible.

"This plan will take into consideration the special case of the city of Mosul, the complications of the city and the possible surprises that might happen during the operation," al-Jaafari said.

Such an optimistic assessment, however, would appear to signal a split between Iraqi leaders and U.S. officials who, while pleased with progress on the ground, insist many of the pieces are not even in place.

"If there's any planning to be done, anything we can move in in advance, we — the coalition — recommend that happen before the battle of Mosul even takes place," he added.

U.S. Defense Secretary Ash Carter also raised concerns about planning for Mosul on Wednesday, while visiting with troops at Fort Bragg, North Carolina.

Carter said the U.S., Iraq and Iraqi Kurdish leaders only "have an understanding" of how the envelopment of Mosul will play out.

FILE - In this June 16, 2014, file photo, demonstrators chant pro-Islamic State group slogans as they carry the group's flags in front of the provincial government headquarters in Mosul, Iraq.

"That is going to be a cooperative effort that we are going to galvanize between the Iraqi government and the Peshmerga forces," he said. "We're now discussing what happens in Mosul afterward.

"We're trying to approach the war so that sustainment of victory is built in," Carter said.

Stumbling blocks

For now, the potential pitfalls are numerous.

Officials point out IS has ruled Mosul for the past two years, giving it plenty of time to harden defenses in and around the self-declared caliphate's Iraqi capital.

The terror group's strategy with other cities it has lost will also make for a difficult and slow fight. In both Ramadi and Fallujah, IS left behind a complex web of improvised explosive devices, or IEDs, and booby traps designed to kill Iraqi forces while turning the cities into smoldering ruins.

Despite reports that many top IS officials and foreign fighters have already fled Mosul, the group is still believed to have a strong presence in the city.

Iraq's foreign ministry estimated as many as tens of thousands of IS fighters are holding out in the city and its environs, though other Iraqi militia leaders and U.S. officials believe the number is closer to about 8,000.

Intelligence officials and Iraqi militia leaders also say IS has been doing all it can to scare Mosul's Sunni residents, trying to convince them the Iraqi government will not protect them from the Shia militias accused of targeting Sunnis during the campaign to reclaim Fallujah.

The noose tightens

Still, Iraq’s foreign minister remains undaunted.

"We have no problem with the community, the original community of the city of Mosul," he said, insisting the diverse groups, including the Sunnis, "are with liberating their city."

FILE - Displaced children, who fled from the Islamic State violence, gather at a refugee camp in the Makhmour area near Mosul, Iraq, June 17, 2016.

"The executions that happen in the city from time to time prove that there's resistance from inside the city," al-Jaafari said.

"Whether Daesh is defeated in Mosul at the end of the year or early during the next year, this makes no difference because the result is the same," he said, using the Arabic acronym for the terror group. "Daesh will be defeated totally in Iraq."

U.S. officials estimate there are still about one million civilians left in Mosul. And United Nations officials warn that once the battle to retake Mosul begins in earnest, hundreds of thousands will flee the city, setting the stage for what could be the largest humanitarian relief operation this year.

"The noose, if you will, has been tightening around Mosul for now probably seven or eight weeks with the performance of the Iraqi security forces," Chairman of the Joint Chiefs of Staff, Gen. Joseph Dunford, told Pentagon reporters Monday. "But the pace of the operation is driven by Iraqi capability and Iraqi political decision-making."